It is known to analyze a patient's vertebral column in reference to so-called “pelvic” parameters that are documented in the scientific literature. The appended FIG. 1 very diagrammatically shows the base of a vertebral column, i.e., a part of the lumbar vertebrae L and the sacrum S, as well as the femoral heads TF; said pelvic criteria are:
the SS (sacral slope) criterion, which is the incline angle of the plate of S1 (first vertebra of the sacrum), relative to the horizontal;
the PV (pelvic version) criterion, which is the angle formed by the straight segment connecting the center of the femoral heads TF and the center of the plate of S1 with the vertical;
the PI (pelvic incidence) criterion, which is the angle formed by the straight segment connecting the center of the femoral heads TF and the center of the plate of S1 with the perpendicular to the plate of S1.
It is accepted that an individual will adopt a natural vertebral column posture, called “economic”, avoiding pain and other pathologies, if his pelvic parameters in particular are in agreement with his back morphotype. If this is not the case, surgical treatment may be considered in order to reestablish proper posture of the vertebral column, in which that agreement exists.
It is well known to perform this type of recovery using rigid vertebral rods, in particular metal, fastened to the vertebrae using pedicle screws, which must be curved suitably based on the correction to be done. The publication of patent application No. WO 98/55038 illustrates an equipment of this type.
It has been shown that imparting the appropriate curvature to a straight rod may be very difficult for a surgeon, the curvature being more or less pronounced in any given location of the rod. Currently, such a curvature is done at the surgeon's discretion and calls greatly on the latter's experience and dexterity. The trial and error necessary to obtain an appropriate curvature have the significant drawback of extending the operation time, which is not desirable for the patient, and the risk of implanting a rod with a non-ideal curvature cannot be ruled out.